The present invention relates to means for reducing shear stresses between the stator winding conductor insulation of an air-gap dynamoelectric machine and the adjacent surface of a channel in which the conductor is supported.
Air-gap dynamoelectric machines include stator winding conductors disposed in the air-gap separating the rotor and the stator magnetic core of the machine. Such stator winding conductors have insulation thereon and are supported in channels formed from the adjacent surfaces of the conductor support means. In operation of an air-gap dynamoelectric machine, relative thermal expansion between such an insulated conductor and the adjacent surface of such a channel can give rise to high shear stresses on the insulation, which stresses can damage the insulation and result in dielectric breakdown thereof. One known approach to reducing the problem of shear stresses is to provide low coefficient of friction material between the conductor insulation and the channel surface. This approach, however, is subject to failure where the interface between conductor insulation and a channel surface has been contaminated by thermosetting resin applied to portions of the air-gap dynamoelectric machine during the manufacturing thereof, whereby the insulation becomes bonded to the channel surface.
A first known approach to the prevention of thermosetting resin contamination of an interface between conductor insulation and a channel surface in an air-gap dynamoelectric machine is to strive, during manufacturing of the dynamoelectric machine, to prevent excess uncured thermosetting resin from reaching the conductor insulation or channel surface. This approach has been only partially successful owing to the difficulty of precisely limiting the flow of excess uncured resin.
A second known approach to overcoming the problem of contamination of a conductor insulation-channel surface interface by thermosetting resin is to coat the conductor insulation and the channel surface with release agents which form a weak bond to any applied thermosetting resin. This approach, however, is only applicable where the conductor insulation does not have a rough surface, such an an "armor" layer on stator winding conductors, which permits thermosetting resin to "key" into the rough surface.